As shown in FIG. 1, one conventional type of friction clutch system 10 may be found in an automobile for engaging, disengaging and transmitting torque from the engine 12 (i.e., power source) to a transmission 14 (i.e., driven system). By way of example, the conventional automotive friction clutch system 10 includes a thrust or pressure plate 16 mounted within a clutch housing 18 so that the thrust plate 16 cannot rotate within the housing 18, but can move axially within the clutch housing. The housing 18 is mounted to a counterthrust plate 20. Being weighted, the counterthrust plate is also commonly used as a flywheel as well. The flywheel 20 is mounted to and driven by the power source 12, which may take the form of an internal combustion engine, an electric motor, etc.
The pressure plate 16 may be biased or pressed toward the flywheel 20 by one or more partially compressed Belleville springs, (diaphragms), or coil springs (not shown) and may or may not also employ centrifugal clamping force assist (in the form of bob weights, not shown) all of which can be mounted within the housing 18. The assembled combination of the clutch housing 18, the pressure plate 16, and the diaphragm/spring is generally referred to as a pressure plate assembly 22 within the automotive industry.
A friction disc assembly 24 is located between the flywheel 20 and the pressure plate assembly 22. The friction disc assembly 24 includes, in the illustrated example, a floater disc 26 sandwiched between two friction discs 28. The friction discs 28 include friction facings or linings 30, a carrier plate 32 and a splined hub 34. The friction facings 30 bonded or otherwise, are mechanically connected to the carrier plate 32. The carrier plates 32 are coupled by the splined hub 34, which takes the form of an internally splined hub, to an externally splined shaft 36 of the driven member 14.
In FIG. 2, the like components retain the same reference numerals, but the friction clutch system 10 includes a different friction disc assembly 40. As illustrated, the friction disc assembly 40 includes a floater disc 42 sandwiched between two friction discs 44, both having multiple, radially located damper springs 46 for the purpose of smoothing clutch engagement and isolating engine vibrations from the transmission 14 and driveline (not shown). The damper springs 46 are positioned in a sprung hub assembly 48 that extends axially.
For greater torque capacity and improved heat dissipation, a friction clutch system may incorporate multiple friction discs mounted between the pressure plate assembly and the flywheel. For multi-plate clutch designs, the floater or floater plate may be mounted to and driven by the flywheel, with a floater being located between adjacent pair of friction discs. The pressure plate assembly, flywheel and floater also serve as friction surfaces for the friction discs. Because each friction disc assembly typically has two friction surfaces, a two-disc clutch will have four friction surfaces, a three disc clutch will have six friction surfaces, and so on.
The torque capacity of a friction clutch system is defined as the maximum amount of torque that can be transferred through the system while in its fully engaged state. Once the clutch torque capacity has been exceeded, torque can be lost through the unintentional slipping effect caused between the friction surfaces of the friction clutch system components.
The conventional clutch system of FIG. 1 includes two solid hubs, each with internal splines for engaging the shaft of the transmission, but without any damper springs to reduce the spatial envelop and provide a low rotating weight. However, the lack of damper springs to smooth clutch engagement and isolate engine vibrations can, at least eventually, have a detrimental effect on driveline components. In addition, clutch performance and drive-ability of the vehicle may be diminished.
The conventional, multiple disc clutch system of FIG. 2 with the two sprung hub assemblies, both internally splined for engaging the shaft of the transmission may help with isolating engine vibrations, but require a greater spatial envelope and increase the rotating weight of the system. Current space constraints in various vehicles would not provide room for such an arrangement. Consequently, both conventional systems may be undesirable for use as a high-performance clutch system